Beta endorphin is an endogenous opioid peptide hormone released from the pituitary during stress having the same peptide sequence as the 61 to 91 portion of beta lipotropin. This peptide has been recognized as an endogenous morphine-like analgesic.
Gautray et al., Am. J. Obst. Gynecol., 129, 211 (1977) disclosed that amnionic fluid contains a significant amount of beta endorphin as detected by radioimmunoassay (RIA). Further, acid extracts of human placenta have been disclosed by Nakai et al., Life Sci., 23, 2013 (1978) to contain both .beta.-endorphin and ACTH as well as beta lipotropin.